// 具体书籍类（具体享元类）
class ConcreteBook implements Book {
    private final String bookNumber;

    public ConcreteBook(String bookNumber) {
        this.bookNumber = bookNumber;
    }

    @Override
    public void display(String author, String title) {
        System.out.println("书籍编号：" + bookNumber);
        System.out.println("作者：" + author);
        System.out.println("标题：" + title);
        System.out.println();
    }
}
